Priority is claimed on Japanese Patent Application No. 2004-121620, filed Apr. 16, 2004, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a battery monitoring system for monitoring the states of device batteries in a system in which a plurality of devices provided with batteries operate in coordination.
2. Description of Related Art
When displaying the remaining capacity of a battery in a battery-powered video camera and the like, the current remaining capacity with respect to the full charge capacity has conventionally been shown by a five-level battery-shaped mark or by the remaining recording time in minutes. FIG. 6 shows an example of a system in which a plurality of devices provided with batteries operate in coordination. FIG. 6 is a block diagram showing the schematic structure of a conventional imaging system provided with a camera. This imaging system includes a camera 1A, a recording device 2A, and a monitor 3A, with each constitution shown in the drawing explained below.
The camera 1A is a professional-use video camera such as a television camera. An imaging portion 10A in the camera 1A images a subject and generates image data constituting a moving image. A battery 11A supplies driving power to each portion in the camera 1A. A display portion 12A, which functions as a finder, displays the image picked up by the imaging portion 10A. The display portion 12A displays the state of battery 11A together with the image. A control portion 13A outputs the image data generated by the imaging portion 10A to the recording device 2A via an interface not shown.
The control portion 13A detects the voltage of the battery 11A and calculates the remaining capacity of the battery 11A based on this voltage. The control portion 13A calculates as needed the remaining time that the camera 1A can run on the battery 11A (remaining operating time) based on the remaining capacity of the battery 11A. Also, the control portion 13A combines the display data, for displaying the remaining capacity and remaining operating time in the display portion 12A, with the image data, and, based on the combined data, generates an image signal for driving the display circuit in the display portion 12A and outputs it to the display portion 12A.
A battery 20A in the recording device 2A supplies driving power to each portion in the recording device 2A. A control portion 21A stores image data output from the camera 1A and input via the interface in a storage unit such as a hard disk drive not shown. It also outputs the image data to the monitor 3A via another interface not shown. The control portion 21A detects the voltage of the battery 20A and calculates the remaining capacity of the battery 20A based on this voltage. The control portion 21A calculates as needed the remaining time that the recording device 2A can run on the battery 20A based on the remaining capacity of the battery 20A.
The control portion 21A creates display data for displaying the remaining operating time in a display portion 22A and, based on this display data, generates a display signal for driving the display circuit in the display portion 22A and outputs it to the display portion 22A. The display portion 22A displays the remaining operating time based on the display signal. The monitor 3A displays an image based on the image data output from the recording device 2A. While there are cases of the recording device 2A not being provided with the display portion 22A, the explanation given here assumes the case of the display portion 22A being provided.
With the aforementioned constitution, the remaining capacity of the battery 11A and the remaining operating time that is possible with the remaining capacity are shown in the display portion 12A of the camera 1A. The display portion 12A displays the remaining capacity, which is indicated for example by a battery mark, and the remaining operating time to be 30 minutes. In addition, the display portion 22A of the recording device 2A displays the remaining operating time, during which operation is possible with the remaining capacity of the battery 20A, to be 50 minutes.
Japanese Unexamined Application, First Patent Publication No. 2000-32100 and Japanese Unexamined Application, First Patent Publication No. 2003-153453 disclose technology for monitoring the state of a battery. Japanese Unexamined Application, First Patent Publication No. 2000-32100 discloses technology to monitor the voltages of batteries in a device provided with at least 2 batteries, select the battery having the least remaining capacity that exceeds a reference voltage level, and switch to the selected battery. Japanese Unexamined Application, First Patent Publication No. 2003-153453 discloses technology in which a small electrical apparatus powered by a secondary battery informs external equipment of the remaining capacity of the secondary battery, and the informed external equipment displays the remaining capacity of the secondary battery of the small electrical apparatus.
In the conventional system shown in FIG. 6, each device equipped with a battery shows the remaining capacity (or remaining time) of its battery. Because the camera 1A and the recording device 2A are powered by their own batteries, the user must therefore individually check the remaining battery level of each device. In the example shown in FIG. 6, the camera 1A has 30 minutes of remaining operating time with the battery 11A, while the recording device 2A has 50 minutes of remaining operating time with the battery 20A. Therefore, the remaining operating time for the entire system that can record images picked up by the camera 1A on the recording device 2A is 30 minutes.